1. Field of the Invention
The present invention relates to a novel cyclohexenylethane compound, and more specifically, it relates to a novel cyclohexenylethane derivative which is suitable as one component of an electro-optical display material, and a liquid crystal composition containing this derivative.
2. Description of Related Art
In recent years, a liquid crystal has become more and more important as a dielectric for a display element because of an electro optical effect based on the anisotropy of a dielectric constant and a refractive index. As display systems for the liquid crystal, there are, for example, a dynamic scattering system, a phase transition system, a DAP system, a guest/host system, a TN system using a 90.degree. twisted cell, an STN or SBE system using a 180.degree.-270.degree. twisted cell and an active matrix system using TFT to which much attention is paid of late. Liquid crystal materials used in these display systems are required to have various characteristics. For example, each liquid crystal material should have a wide temperature range in which a liquid crystal phase is maintained; it should be stable to environmental factors (e.g., moisture, heat, air, light and electricity); it should be colorless; its anisotropy quantity (hereinafter abbreviated as ".DELTA.n") of a refractive index should be a suitable value; its elastic constant ratio should be high (or low); its anisotropy quantity (hereinafter abbreviated as ".DELTA..epsilon.") of a dielectric constant should be large; its viscosity should be low; and its specific resistance ratio should be high and the change of this ratio with time should be slight.
Presently, however, no single compound can drive the display element sufficiently by itself, and in fact, a liquid crystal mixture prepared by mixing several kinds of liquid crystal-like compounds is used. For this reason, it is required that the liquid crystal-like compounds have a good compatibility with other liquid crystal compounds.
In this specification, the term "liquid crystal-like compound" means the liquid crystal compound or a compound having a certain function to drive the liquid crystal display element.
Nowadays, a compound having a cyclohexene ring has been introduced as the liquid crystal. For example, Japanese Laid-open Patent Publication No. 1-106830 and DE 3717397A1 disclose ##STR2##
wherein R' is an alkyl group or the like, but in this compound, the upper limit temperature for the liquid crystal phase is low in spite of it being a tricyclic compound.
In addition, U.S. Pat. No. 4405488 discloses a compound represented by the formula ##STR3## wherein R is an alkyl group, but this compound is unstable to environmental factors.